Title

Author

Degree Type

Thesis

Date of Award

2011

Degree Name

Master of Science

Department

Agronomy

First Advisor

Allen Knapp

Second Advisor

Jode Edwards

Abstract

Hybrid maize yield increases, new product development, and increased stress tolerance can be more easily achieved with a better understanding of the physiological and genetic basis for phenotypic changes in response to recurrent selection for yield. The purpose of this study was to identify changes in grain fill characteristics and their interaction with plant density in a closed population and identify a model that accurately predicts grain fill in this population. We hypothesize that recurrent selection for increased yield indirectly impacted the grain fill characteristics of maize including final kernel weight, kernel fill duration, and kernel fill rate in the Iowa Stiff Stalk Synthetic maize population. We also hypothesize that recurrent selection for yield has indirectly improved maize tolerance to high plant density stress for these grain fill characteristics.

Populations representing different levels of advancement from the Iowa Stiff Stalk Synthetic maize population were compared to at two different locations near Ames, Iowa in 2009 and 2010. Populations were compared at plant densities of 5.3 and 7.7 seeds m-2. Treatments were replicated three times per location in a split plot design. Recurrent selection for yield has led to changes in final kernel weight and kernel fill duration, as well as the response of kernel weight to increased planting densities. This supports our hypothesis that recurrent selection for yield changed grain fill characteristics and the effect of high plant density stress in the Iowa Stiff Stalk Synthetic maize population. The rate of kernel fill was not affected by recurrent selection for yield in the Iowa Stiff Stalk Synthetic maize population.